CS4812 Cirrus Logic, CS4812 Datasheet - Page 17

• Manufacturer Part Number: CS4812
• Description: Fixed Function Multi-Effects Audio Processor
• Manufacturer: Cirrus Logic

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3. FUNCTIONAL DESCRIPTION
3.1
The CS4812 is a complete audio subsystem on a
chip, integrating an DSP with on-chip RAM, two
24-bit ADCs, two 24-bit DACs, and a serial control
port.
The sigma-delta ADCs include linear phase digital
anti-aliasing filters and only require a single-pole
external passive filter.
The sigma-delta DACs include analog switched-
capacitor anti-image filters and require an external
second or third order active filter that can be easily
integrated into an output differential-to-single-end-
ed converter circuit.
The serial control port is designed to accommodate
I
slave mode. It allows interfacing to external non-
volatile memory for stand-alone operation or to a
host-controller for real-time control. All communi-
cations between the DSP and an external EEPROM
or host-controller are handled through the serial
control port.
DS291PP3
2
C
®
or SPI interfaces and can operate in master or
Overview
(2 Vrms max)
CMOUT
input signal
+
-
10 µ F
Figure 10. Recommended Line Input Buffer
+
10 k
-
+
4.7 k
+
10 µ f
10 k
0.1 µ F
3.2
3.2.1
AINR+, AINR-, AINL+, and AINL- are the line
level analog inputs (See Figure 5). These pins are
internally biased to the CMOUT voltage of 2.3 V.
A DC blocking capacitor placed in series with the
input pins allows signals centered around 0 V to be
input to the CS4812. Figure 5 shows operation with
a single-ended input source. This source may be
supplied to either the positive or negative input as
long as the unused input is connected to ground
through capacitors as shown. When operated with
single-ended inputs, distortion will increase at in-
put levels higher than -1 dBFS. If better perfor-
mance is required, a single-ended-to-differential
converter, shown in Figure 10, may be used. It pro-
vides unity gain, DC blocking and anti-alias filter-
ing.
Inputs may be externally AC or DC coupled. This
permits use of the ADCs for input of audio signals
or for measurement of DC control voltages. By de-
fault, an internal high pass filter removes any DC
offsets from both of the ADC inputs. If measure-
ment of DC is required on either of the ADC inputs,
then the on-chip high pass filter must be disabled.
Analog audio input signals that are DC coupled
must be biased at 2.3 V to maintain proper input
+
-
10 k
GND
+5 V
Analog Inputs
Line Level Inputs
150
150
2.2 nf
AIN -
AIN +
CS4812
17